1. Field of the Invention
The present invention relates to a magnetic recording medium suitable as a recording medium for a hard disc device.
2. Discussion of Background
In recent years, magnetic recording media have been developed for high density recording, As one of methods for reducing media noises, JP-A63-146219 or IEEE TRANSACTIONS ON MAGNETICS, 26(5), 2700-2705(1990) discloses that a magnetic recording film is made to have a multilayer structure comprising a plurality of magnetic layers and an interlayer interposed between the adjacent magnetic layers to reduce the magnetic interaction between the adjacent magnetic layers. Further, as a means to obtain a high coercive force for high recording density, it has been reported to employ, as an underlayer, NiAl having B2 crystal structure (IEEE TRANSACTIONS ON MAGNETICS, 30 (6), 3951-3953 (1994), EP0704839A1).
In said LP-A-63-146219, in order to reduce noises, an Al2O3, SiO2 or Cr film has been studied as the interlayer to be used for a magnetic recording medium having the above-mentioned magnetic recording film having a multilayer structure, but reduction of noises is still inadequate for an application in future wherein a GMR head will be used. In said EP0704839A1, NiAl has been studied as the underlayer, but no study has been made to let the magnetic recording film have a multilayer structure comprising a plurality of magnetic layers and an interlayer interposed between the adjacent magnetic layers to reduce the magnetic interaction.
It is an object of the present invention to provide a magnetic recording medium having a medium noise substantially reduced and being capable of high density recording.
The present invention has been made to accomplish the above object and provides a magnetic recording medium comprising a non-ferromagnetic substrate and a magnetic recording film formed on the substrate with an underlayer interposed therebetween, wherein the magnetic recording film comprises a plurality of magnetic layers and an interlayer made of a material having a B2 crystal structure or an interlayer made of Ru, disposed between the adjacent magnetic layers.